Optical communication involves the transmission of data in which light is used as the transmission medium. An optical communication system comprises an optical transmitter, a channel (e.g., an optical fiber), and an optical receiver. The optical transmitter encodes data onto an optical signal (light wave), the channel carries the optical signal from the transmitter to the receiver, and the receiver extracts the data from the received optical signal.
One specific type of optical communication is coherent optical communication. In coherent optical communication, the transmitter encodes the data onto the electrical field of the optical signal. At the receiver, the data is extracted through direct measurement of the complex electrical field.